The effects of third-order torque and self - Saint Louis University

archwires. At binding angulations, two contacts form at
the ends of the bracket-slot, one on the occlusal face of
the wire and one on the gingival face. As the wire
deflects upon activation, those wires with a greater
modulus of elasticity will produce larger normal bracket-
wire contact forces at those contact points. 5,48 Several
investigations have found that ß-titanium alloy wires have
greater resistance to sliding than either stainless steel
or nickel-titanium alloy wires, particularly in the absence
of binding. 18,20-24,26,27,29,35,36 Tspelepsis and associates 33
failed to detect any such differences across the three
alloys.
Surface Characteristics
Frank and Nikolai 5 found that, with small, nonbinding
angulations and in stainless steel slots, stainless steel
wires exhibited less sliding frictional resistance than
nickel-titanium alloy wires. This difference was thought
to be related to the roughness of the wire-alloy surface.
This property of a wire is determined by characteristics of
the alloy, the manufacturing process, any surface treatment
and, for some materials, the shelf-time and/or use-time. 5
Other researchers have speculated that the greater friction
produced by titanium alloy wires when compared to stainless
11